New types of communication systems, as well as improvements to existing communication systems, have been permitted as a result of advancements in communication technologies. Such new communication systems, or existing communication systems that include improvements, generally permit larger amounts of, and additional types of, data to be communicated at increased throughput rates. New communication services, requiring, e.g., high data throughput rates are possible through the use of such new and improved communication systems.
Advancements in digital communication techniques, for instance, are amongst the advancements in communication technologies that have permitted new communication systems and improvements to existing communication systems. When digital communication techniques are used, data that is to be communicated is digitized. And, the digitized data, so-formed, is formatted in a selected manner, prior to communication thereof. The digital data is formatted, typically into packetized form. The packetized, digital data is referred to as packet data, formed of data packets. Individual ones of the data packets can be communicated at discrete intervals to effectuate communication of the data pursuant to a communication service.
Various protocol schemes have been promulgated by which to standardize the formatting of the digitized data into data packets. And, more than one formatting protocol is sometimes used in the formation of a single data packet. That is to say, multiple-levels, or layers, of formatting of the digitized data are sometimes provided.
A communication device used to communicate data, either to send the data or to receive the data, can be represented in logical-layer form. Such representation, as appropriate, includes layers at which formatting is applied to, or removed from, digitized data. A user datagram protocol (UDP), or UDP protocol, is an exemplary protocol scheme that is widely utilized. UDP formatted data is regularly communicated, for instance, in the effectuation of real-time communication services. Conventional UDP-formatting of data advantageously provides for sending-station-specified data rates. And, data packets delivered to a receiving station are delivered immediately to a receiving application irrespective of their order of arrival. In conventional UDP formatting, a checksum is used to verify UDP header and payload data parts, thereby to effectuate validation of received data packets. Conventional UDP checksum protection provides protection for an entire payload portion of a UDP-formatted data packet or for none of the payload portion of the data packet.
With the advent of packet radio communication systems in which an air interface is defined upon which to communicate packetized data between sending and receiving stations, a modified UDP formatting scheme, referred to as UDP-Lite, is sometimes used. The UDP-Lite scheme is compatible with the conventional UDP formatting scheme and is intended further to provide improved functionality and flexibility needed for communications in a radio environment.
A UDP-Lite-formatted data packet differs with a conventional, UDP-formatted packet in that the UDP length and checksum is replaced with a partial coverage length and partial checksum. Thereby, the data contained in the UDP-Lite data packet is separated into protected and unprotected sections. Pursuant to checksum calculations, when an error is detected in the protected part, the data packet is discarded. However, errors contained in the unprotected part of the data packet do not cause the data packet to be discarded, and, instead, the data packet is provided to an application layer of the receiving station at which the data packet is received.
Passing of data to an application layer irrespective of whether the data contains errors is generally advantageous in real-time applications, such as audio, video, or image communication applications. However, there may be times in which detection of errors should be detected and not necessarily immediately passed to the application layer. For instance, a video data packet, i.e., a data packet containing information used pursuant to effectuation of a video communication service, might be formed, sequentially, of header information, macro-block information, DC coefficients, and AC coefficients. When formatted as a UDP-Lite packet, the checksum can be defined such that the header information, the macro-block information, and the DC coefficients are protected while the AC coefficients are left unprotected. If, though, the non-protected part of the data packet is corrupted during its communication to a receiving station and the application level layer is unaware of the corrupted data, processing of the corrupted data might be more problematic than discarding the data.
If a second checksum were provided for the data packet, the corrupted data would be detected and the data packet could be discarded. If a manner could be provided, therefore, by which to provide a second checksum protection to this additional portion of the UDP-Lite data packet, improved communications could be provided.
More generally, a data packet construction providing for multiple checksum protection would permit multiple portions of the data packet to be checksum protected.
It is in light of this background information related to the communication of packet-formatted data that the improvements of the present invention have evolved.